Between six and eight weeks kittens are fully weaned from their mothers milk and can eat dry or wet kitten food. I got her at about 4 12 months old and since I have had her she has been on a mostly canned diet. Kitten food contains more calories than adult cat food.
Adult food is lower in protein and fat than kitten food so the little guy compensated by eating more. At this stage kittens still need about twice as many calories per pound than adult cats. The answer is NO If you keep feeding adult cat foods to kittens you may deprive them of getting vital minerals and vitamins required for their healthy metabolism. Sometimes vets ask you to wait till your cat is about 1 year old.